class Solution {
public:
    TreeNode* mergeTrees(TreeNode* t1, TreeNode* t2)
    {
        if (t1 == nullptr)
        {
            return t2;
        }
        if (t2 == nullptr)
        {
            return t1;
        }
        TreeNode* merged = new TreeNode(t1->val + t2->val);
        merged->left = mergeTrees(t1->left, t2->left);
        merged->right = mergeTrees(t1->right, t2->right);
        return merged;
    }
};